The present invention relates generally to cooling systems for electrical component enclosures, and in particular to a method and apparatus to prevent flow recirculation during failure of an air moving device used to cool electrical or other components within an enclosure.
Electronic cooling systems designed for high availability or continuous operation often employ redundant air moving devices (e.g., fans or blowers) that are arranged in parallel. This arrangement is used to guard against catastrophic loss of cooling flow in the event of a single blower failure. One problem with this type of parallel blower configuration is that when one blower fails, the pressure difference across the surviving blower pushes air backwards through the failed blower. This reduces the delivered flow rate that would otherwise be available from the surviving blower.
To prevent back flow, the normal practice is to add a flap-type device on the exhaust side of the blowers. Common flapper designs include swinging door flaps and multiple slat vanes. However, the aerodynamic losses created by prior art designs are substantial and must be taken into consideration during system development, because they reduce airflow rate delivery in normal operation. Therefore, although these prior art exhaust side systems prevent recirculation during a blower failure, they inadvertently produce large impedances during normal operation of the blower.
In particular, the volume of air that can be moved through a system can be increased by reducing the total system impedance. By reducing the contribution of the anti-recirulation device losses to the overall system impedance, the system blowers can move more air and thereby increase the cooling capacity of the system, or reduce the acoustic output of the system at similar flow rates achieved at lower blower speeds
Accordingly, a method and apparatus is desired that prevents recirculation during a blower failure while reducing aerodynamic losses within the device.